Fast action on certain pollutants such as black carbon, ground-level ozone and methane may help limit near term global temperature rise and significantly increase the chances of keeping temperature rise below 3.6 degrees F. Protecting the near-term climate is central to significantly cutting the risk of amplified global climate change linked with rapid and extensive loss of Arctic ice on both the land and at sea, said assessment authors including Veerabhadran Ramanathan, a climate and atmospheric scientist at Scripps Institution of Oceanography, UC San Diego.

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The findings, released on June 15 in Bonn, Germany, during a meeting of the UN Framework Convention on Climate Change (UNFCCC) have been compiled by an international team of more than 50 researchers chaired by Drew Shindell of the National Aeronautics and Space Administration (NASA).

Ramanathan is organizing a related briefing today in Washington, D.C., for several federal agencies on how to reduce emissions of global warming pollutants such as carbon dioxide, black carbon and ozone and prevent human deaths from traditional biomass burning cook stoves in developing nations.

Big cuts in emissions of black carbon will improve respiratory health. Close to 2.5 million premature deaths from outdoor air pollution could on average be avoided annually worldwide by 2030 with many of those lives saved being in Asia, it is estimated.

Big cuts in ground level ozone could also contribute to reduced crop damage equal to between 1 to 4 percent of the annual global maize, rice, soybean and wheat production.

Cutting these so-called short-lived climate forcers can have immediate climate, health and agricultural benefits, the report concludes. This is because, unlike carbon dioxide (CO2) which can remain in the atmosphere for centuries, black carbon for example persists only for days or weeks.

The researchers, however, also underline the fact that while fast action on black carbon and ground-level ozone could play a key role in limiting near-term climate, immediate and sustained action to cut back CO2 is crucial if temperature rises are to be limited over the long-term.

It is the combination of action on short-lived climate forcers and long-lived greenhouse gases which improves the chances of keeping below the 2-degree target throughout the 21st century.

Black carbon is a major component of soot and is formed from the incomplete combustion of fossil fuels, wood and biomass. Key sources include emissions from cars and trucks, cookstoves, forest fires and some industrial facilities. It affects the climate by intercepting and absorbing sunlight and darkens snow and ice when deposited, while also influencing cloud formation.

Scripps Institution of Oceanography have previously stated that soot and other forms of black carbon could cause as much as 60 percent of the current global warming effect of carbon dioxide, more than that of any greenhouse gas besides CO2.

The troposphere extends from the surface of the Earth to between 10 and 18 kilometers above the surface of the Earth and consists of many layers. Ozone is more concentrated above the mixing layer, or ground layer. Ground-level ozone, though less concentrated than ozone aloft, is more of a problem because of its health effects.

Tropospheric ozone is a greenhouse gas and initiates the chemical removal of methane and other hydrocarbons from the atmosphere. Thus, its concentration affects how long these compounds remain in the air.